Senior European intelligence officials tell NBC News that France's ability to prevent attacks like Friday's massacre is now challenged by the increasing ability of ISIS to operate under the radar, as a squad of jihadi cybergeeks train would-be terrorists how to keep their electronic communications secret.
One senior European counterterrorism official said the region's authorities have been "alarmed for quite some time" at ISIS' use of young cyber experts to stay several steps ahead of law enforcement.
"When you look at how sophisticated Daesh is in its use of social networks," he said, using an Arabic name for ISIS, "it suggests that there are geeks behind this. … Among the foreign [ISIS] fighters, you have people who are IT savvy [and] keep up with the technological developments."
Officials believe the ISIS geek squad is teaching terrorists how to use encryption and communication platforms like Silent Circle, Telegram and WhatsApp.
Aaron F. Brantly said he and his colleagues at the U.S. Army-affiliated Combating Terrorism Center have found that Islamic State members use as many as 120 separate platforms, many of them encrypted, to communicate and share information. One of its most favored methods, he said, is a highly encrypted form of communication called Telegram.
"It essentially allows them to hide what they are discussing from people who aren't explicitly looking for it," especially law enforcement and intelligence agencies, Brantly said. "Obviously this is a major concern. … They are creating a space for themselves to operate independent of direct surveillance."
The senior European counterterrorism official said that European authorities are gravely concerned and will meet this week to discuss the issue - though they are already becoming contentious with each other about their lack of options. Some are restricted by civil liberties concerns in their home countries, while others note that creating a "back door" in an electronic communication platform - meaning a way for governments to spy on messages in real time - also creates an opportunity for non-governmental groups to take a peek. When Greece put a "back door" in electronic communications passing through its territories, it was quickly exploited by hackers.
"I am waiting for somebody to show me a way we can do this that is guaranteed to be only used by the good guys," said Paul Rosenzweig, a cyber consultant and former deputy assistant secretary in the U.S. Department of Homeland Security. "But it is not person-specific. Anything that we can create can, and will, be cracked."
Jihadis have always used whatever communication platforms are available as soon as they become available. Officials have monitored multiplayer on-line games like World of Warcraft for jihadi meetups, and also believe that they use gaming consoles like PlayStation 4 to converse with each other. Rosenzweig said that jihadis also used to use Second Life, an on-line virtual world created more than a decade ago, to communicate and perhaps even to transfer money.
Rosenzweig said that U.S. officials have been concerned about ISIS and al Qaeda use of newer secure communications platforms like WhatsApp and Telegram for as long as they have existed.
"It's like trying to stop the tide," he said. "It is inevitable. We are going to have to get used to living in a world where both the bad guys and the good guys have unbreachable communications systems."
France, which has weathered a series of terror attacks in 2015, starting with the Charlie Hebdo massacre, is also made vulnerable by the technological limitations of its security services.
The French have less ability to spy on electronic telecommunications than other Western powers. Their "signals intelligence" capability, said another European intelligence official, "is nowhere near where the U.S. and the U.K. are."
But other experts noted that the French security services have performed much better in an older technology - human intelligence. Since 9/11, France has ramped up its counter-terrorism capacity significantly, and its network of informants and spies have deeply penetrated the country's Muslim community, which is 5 million strong.
These human assets have allowed French authorities to uncover a wide variety of radicals, terrorist sympathizers and recruits for al Qaeda and ISIS - and they are now being mobilized in the hunt for co-conspirators in Friday's attacks.